Eating your greens rather than carrots could be the key to good night-time vision, according to scientists in the US. Ilyas Washington and colleagues at Columbia University, New York, have shown that a chlorophyll derivative can enhance eye sensitivity to red light.

Chlorophyll derivative chlorine e6 enhances eye sensitivity to red light

In sight, light activates a visual pigment that sends an electrical signal to the brain. This process happens in the retina in cone and rod cells. Rod cells are insensitive to colour and the cone cells are mainly responsible for our colour vision. However, in dim light the cone cells cannot function and we largely perceive the world in black and white. This also means we are dependent on rod cells to see in the dark. Since these cells are particularly insensitive at the red end of the visible spectrum, Washington asked: 'How might one enhance red light night-time vision?'

Prompted by research suggesting that deep-sea dragonfish see using chlorophyll, the scientists gave mice a chlorophyll derivative, chlorin e₆, to see if their red vision was improved. Using a technique called electroretinography, which measures retinal cell responses to a flash of light, the researchers found that the treated mice showed almost double the response to red light when compared to non-treated mice. The group also showed that the chlorin e₆ was localised in the retina and conclude that the increased visual sensitivity is a result of light absorption by the chlorophyll derivative.

Washington is currently performing similar research in people. It is possible that taking a chlorophyll derivative supplement could improve night vision, he said.

Nicola Burton